A voltage reference is typically provided by electronic circuitry that outputs a constant voltage despite variations in temperature or power supply that might normally or otherwise cause voltage fluctuations. As a result, the desired behavior is that the voltage reference remains constant even as conditions in the system vary. Such voltage references may be used in power supply voltage regulators, analog-to-digital converters, digital-to-analog converters, and the like as well as many other measurement and control systems.
Almost all integrated circuit devices require a precise voltage reference. One implementation is known as the Brokaw voltage reference, which generally provides a voltage reference between 1.2 and 1.3 V (i.e., about 1.25 V) and consequently necessitates a slightly higher input voltage (e.g., about 1.4 V). However, integrated circuit devices that require voltage references lower than 1.2 V, such as those in mobile applications, are not compatible with the Brokaw voltage reference.
Previous attempts have been made to provide suitable low voltage references such as the depletion NMOS voltage reference. However, such low voltage references have much higher spread due to manufacturing variations, and trimming is required to obtain the desired precision. Trimming is expensive in terms of die area, equipment, and test time.